3-2-1 Principle of Location

The 3-2-1 principle of location (six point location principle) is used to constrain the movement of workpiece along the three axes XX, YY, and ZZ. This is achieved by providing six locating points, 3 pins in base plate, 2 pins in vertical plane and 1 pin in a plane which is perpendicular to first two planes.

Degree of freedom controlled by 3-2-1 location principle

Pins A, B, C on the base plane ( a plane parallel to the plane which contains X and Y axis) restrict the rotation of component about X axis and Y axis. It also limit the downward movement of component along z axis. Ie. 1,2,3,4 and 5 degrees of freedom is restricted.

Pins D, E is in plane parallel to the plane containing X and Z axes. It prevents the rotation of component about Z axis (6, 7 degree of freedom) and the movement of the body in along Y axis towards one direction (8 degree of freedom).

The last pin F is in a plane parallel to plane contains Y and Z axes. It restricts the movement component along X axis in one direction.

Three remaining degree of freedom 10, 11, 12 is unrestricted. It facilitates the loading of the component in the fixture. This three degree of freedom may restrict after loading of component by using clamping devices.